Y / ZSM-5 composite molecular sieve, preparation method thereof and FCC (fluid catalytic cracking) catalyst

Abstract

The invention provides a Y / ZSM-5 composite molecular sieve, a preparation method thereof and an FCC (fluid catalytic cracking) catalyst. The preparation method comprises the following steps: mixing a raw material Y molecular sieve with an acidic treatment agent, and carrying out an acid pickling reaction to obtain an intermediate Y molecular sieve; mixing the middle Y molecular sieve with an alkaline solution of a structure-directing agent, and crystallizing to obtain a Y / ZSM-5 composite molecular sieve; wherein the silica-alumina ratio of the raw material Y molecular sieve is greater than or equal to 2, the acid treatment agent comprises acid, and the mass ratio of the raw material Y molecular sieve to the acid is (0.1-1): (0.01-2); the temperature of the pickling reaction is 85 DEG C, and the time of the pickling reaction is 2 hours. The invention also provides the Y / ZSM-5 composite molecular sieve obtained by the preparation method and an FCC catalyst comprising the Y / ZSM-5 composite molecular sieve. The Y / ZSM-5 composite molecular sieve provided by the invention has two molecular sieve phases, the ratio of the two phases is adjustable, and the Y / ZSM-5 composite molecular sieve has relatively high catalytic performance.

Description

Technical Field

[0001] The invention relates to the technical field of composite molecular sieve synthesis, and in particular to a Y / ZSM-5 composite molecular sieve and a preparation method thereof and an FCC catalyst. Background Art

[0002] For FCC catalysts, there is currently a need for catalysts with good heavy oil conversion capacity, less dry gas, less coking, and good selectivity for light olefins to match other process and technical conditions.

[0003] The current method for preparing FCC catalysts includes hydrothermal treatment. However, hydrothermal treatment has problems such as secondary pore formation and volume limitation, limited mesopore size (usually around 20 nm), and isolated and unconnected mesopores. It is necessary to improve the preparation method of FCC catalysts to increase the mesoporosity and pore connectivity of FCC catalysts.

[0004] At present, refineries are in urgent need of transforming from mainly producing fuel to producing more chemical raw materials. This requires that the current FCC unit should not only have excellent residual oil processing capabilities, but also be able to produce more low-carbon olefins. For FCC catalysts, catalysts with a single molecular sieve phase cannot meet the above requirements. It is necessary to use a composite phase molecular sieve to further crack the straight-chain hydrocarbons and simple isomerized hydrocarbons in the gasoline fraction into smaller molecules, so that the FCC unit can produce more low-carbon olefins such as propylene and butene. This requires regulating the spatial position of the two phases in the composite phase molecular sieve so that there is a synergistic catalytic effect between the two phases to avoid the two phases being too independent and participating in the heavy oil macromolecule conversion process alone.

[0005] At present, the synthesis method commonly used for synthesizing composite phase molecular sieves is generally to form the first molecular sieve by early crystallization, and then continue to crystallize after adding silicon source, aluminum source and structure directing agent in the above system, in order to grow another molecular sieve in situ on the surface of the previous molecular sieve. However, due to the limitations of the synthesis system, the degree of in-situ growth of the second phase molecular sieve cannot be guaranteed, the silicon-aluminum ratio (Si / Al) of the previous molecular sieve skeleton obtained will not exceed 3, and the two-phase molecular sieve formed is generally a large-grained and non-mesoporous micron molecular sieve, and the subsequent ion exchange, hydrothermal treatment, mesoporous introduction and other operation steps are still indispensable. In addition, the existing composite molecular sieve synthesis method cannot solve the problem of synergistic catalysis of the two-phase molecular sieve well, mainly because the above-mentioned synthesis method cannot achieve close contact and uniform dispersion of the two molecular sieves at the nanoscale. In addition, the existing synthesis method cannot adjust the ratio of the two phases in the composite molecular sieve, which makes the composite molecular sieve product type single, and the catalyst user has no choice when selecting such composite molecular sieve products.

[0006] Therefore, it is necessary to provide a method for synthesizing a composite molecular sieve with an adjustable ratio of two-phase molecular sieves. Summary of the invention

[0007] In order to solve the above problems, the purpose of the present invention is to provide a Y / ZSM-5 composite molecular sieve and its preparation method and FCC catalyst. The preparation method provided by the present invention can adjust the ratio of different molecular sieve phases in the composite molecular sieve product to prepare an FCC catalyst with excellent performance.

[0008] In order to achieve the above object, the present invention provides a method for preparing a Y / ZSM-5 composite molecular sieve, the preparation method comprising:

[0009] Mixing a raw material Y molecular sieve with an acidic treatment agent to form a first raw material, and subjecting the first raw material to an acid washing reaction to obtain an intermediate Y molecular sieve;

[0010] The intermediate Y molecular sieve is mixed with an alkaline solution of a structure directing agent to form a second raw material, and crystallized to obtain the Y / ZSM-5 composite molecular sieve;

[0011] Wherein, the silicon-to-aluminum ratio of the raw material Y molecular sieve (the silicon-to-aluminum ratio in the present invention is the molar ratio of Si / Al in the molecular sieve) is greater than or equal to 2;

[0012] The acidic treatment agent includes acid, and the mass ratio of the raw material Y molecular sieve to the acid is 0.1-1:0.01-2.

[0013] In the above preparation method, the acidic modifier and the raw material Y molecular sieve are subjected to pickling reaction, which can, on the one hand, dealumination of the raw material Y molecular sieve and increase the silicon-aluminum ratio of the Y molecular sieve. No migration of the Y molecular sieve skeleton atoms occurs during the pickling reaction, and the positions of the Y molecular sieve skeleton atoms remain unchanged, and the additional effect of dealumination and silicon supplementation will not be produced, and the original microporous properties of the Y molecular sieve will be retained; on the other hand, structural defects such as hydroxyl pit defects can be introduced into the Y molecular sieve to improve the solubility of the Y molecular sieve skeleton, thereby forming mesopores in the Y molecular sieve, providing the raw materials required for the growth of the ZSM-5 molecular sieve, and promoting the solid phase crystallization of the Y molecular sieve and the generation of the ZSM-5 molecular sieve phase. Further, by increasing the silicon-aluminum ratio of the Y molecular sieve, it is beneficial to increase the relative proportion of the ZSM-5 molecular sieve phase in the Y / ZSM-5 composite molecular sieve, thereby realizing the ratio modulation of the Y and ZSM-5 phases in the composite molecular sieve.

[0014] In the above preparation method, after the raw material Y molecular sieve reacts with the acidic treating agent, the silicon-aluminum ratio of the obtained intermediate Y molecular sieve can reach 6-50, for example, it can reach specific values ​​such as 6, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25, 30, 35, 40, 45, 50, and a range with any two of the above specific values ​​as endpoints.

[0015] Conventional hydrothermal synthesis methods make it difficult to achieve continuous adjustment of the silicon-aluminum ratio of Y molecular sieves, and the silicon-aluminum ratio of the obtained Y molecular sieves is limited, usually below 3; and although hydrothermal dealumination can change the silicon-aluminum ratio of Y molecular sieves, it will cause the positions of the atoms in the Y molecular sieve framework to change. The present invention uses a wet chemical method to chemically dealuminate Y molecular sieves of any silicon-aluminum ratio by adjusting the amount of acid without changing the positions of the atoms in the Y molecular sieve framework, thereby achieving continuous and precise adjustment of the silicon-aluminum ratio of Y molecular sieves, while effectively introducing structural defects such as hydroxyl pits while improving the silicon-aluminum ratio of Y molecular sieves, thereby promoting the formation of mesopores in Y molecular sieves and the crystallization of Y molecular sieves, and will not change the atomic positions in the Y molecular sieve framework.

[0016] In the above preparation method, the mass ratio of the raw material Y molecular sieve to the acid is usually controlled to be 0.1-1: 0.01-2, further controlled to be 0.3-0.7: 0.01-2, and further controlled to be 0.3-0.7: 2. In some specific embodiments, in parts by mass, the mass of the raw material Y molecular sieve can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and other specific values ​​and ranges with any two of the above specific values ​​as endpoints; accordingly, the mass of the acid can be 0.01 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts and other specific values ​​and ranges with any two of the above specific values ​​as endpoints.

[0017] In the above preparation method, the acid in the acidic treating agent can remove part of the aluminum in the raw material Y molecular sieve and produce hydroxyl pit defects in the Y molecular sieve. In some specific embodiments, the acid includes an inorganic acid and / or an organic acid.

[0018] In some specific embodiments, the inorganic acid includes one or a combination of two or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0019] In some specific embodiments, the organic acid includes one or a combination of two or more organic acids such as oxalic acid, citric acid, tartaric acid, acetic acid, EDTA, etc.

[0020] Different from the prior art method of preparing composite molecular sieves by using Y molecular sieves with a high silicon-aluminum ratio (greater than 10), the present invention can adjust the silicon-aluminum ratio of the Y molecular sieve to a large extent through the acid washing process without affecting the atomic positions of the molecular sieve skeleton even for the raw material Y molecular sieve with a low silicon-aluminum ratio, so that the silicon-aluminum ratio of the intermediate Y molecular sieve can be continuously and accurately changed within the range of 6-50.

[0021] In the above preparation method, the silicon-aluminum ratio of the raw material Y molecular sieve is generally controlled to be greater than or equal to 2, and can be further controlled to be greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, for example, specific values ​​such as 2, 3, 4, 5, 6, 7, and ranges with any two of the above specific values ​​as endpoints. In some specific embodiments, the silicon-aluminum ratio of the raw material Y molecular sieve can be 2-10, 2-7, etc. The present invention uses the raw material Y molecular sieve with the above silicon-aluminum ratio range, and after being converted into an intermediate Y molecular sieve through an acid washing reaction, the characteristic diffraction peak of the Y-type molecular sieve can still be retained.

[0022] In the above preparation method, the raw material Y molecular sieve includes one or a combination of two or more of USY molecular sieve, NH4Y molecular sieve, HY molecular sieve, and RY molecular sieve (rare earth Y molecular sieve). The present invention has no special requirements for the crystallinity of the raw material Y molecular sieve.

[0023] In the above preparation method, the temperature of the pickling reaction can be 75°C-95°C, specifically 75°C, 80°C, 85°C, 90°C, 95°C and other specific values, as well as a range with any two of the above specific values ​​as endpoints.

[0024] In the above preparation method, the time of the pickling reaction can be specific values ​​such as 1h, 1.5h, 2h, 2.5h, 3h, and a range with any two of the above specific values ​​as endpoints.

[0025] In the above preparation method, the first raw material generally includes a raw material Y molecular sieve and an acidic treatment agent; further, the first raw material may also include an ammonium salt, which can protect the framework of the raw material Y molecular sieve and realize ion exchange. In some specific embodiments, the mass ratio of the raw material Y molecular sieve, acid, and ammonium salt is 0.1-1:0.01-2:0-1 (it can be understood that when the raw material of the intermediate Y molecular sieve includes an ammonium salt, the mass of the ammonium salt is not 0, then the mass range of the ammonium salt in the above ratio is greater than 0 and less than or equal to 1).

[0026] In some specific embodiments, the mass of the raw material Y molecular sieve can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints, and accordingly, the mass of the acid can be 0.01 parts, 0.05 parts, 0.1 parts, 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints, and the mass of the ammonium salt can be 0.01 parts, 0.05 parts, 0.1 parts, 0.5 parts, 1.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints.

[0027] In the above preparation method, the ammonium salt may include one or a combination of two or more of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium oxalate, ammonium fluoride, and ammonium fluorosilicate.

[0028] In the above preparation method, the acidic treatment agent and ammonium salt can be added in the form of a solution, and the solvent in the solution can be water. In some specific embodiments, in the first raw material, the mass ratio of acid, ammonium salt and water can be controlled to be 0.01-2:0-1:10-100.

[0029] In the above preparation method, the intermediate Y molecular sieve is mixed with an alkaline solution of a structure directing agent, so that the structure directing agent can enter the pores of the intermediate Y molecular sieve treated with an acidic treatment agent and dissolve the skeleton structure of the Y molecular sieve to a limited extent. The intermediate Y molecular sieve containing the alkaline solution of the structure directing agent is then directly transferred to a high-temperature closed environment without washing, and the intermediate Y molecular sieve will undergo limited dissolution and in-situ crystallization (specifically solid-phase crystallization) in a high-temperature closed environment, and the silicon-aluminum dissolution of the intermediate Y molecular sieve will cause structural rearrangement, and some of the dissolved molecular sieve fragments will generate ZSM-5 molecular sieves, and finally a Y / ZSM-5 composite molecular sieve with a rich mesoporous structure is obtained.

[0030] In the above preparation method, by controlling the amount of the structure directing agent relative to the intermediate Y molecular sieve and the hydroxide concentration of the alkaline solution of the structure directing agent, the solubility of the intermediate Y molecular sieve can be controlled, so that the Y molecular sieve is dissolved to a limited extent. On the one hand, it can achieve the effect of retaining part of the Y molecular sieve framework and making the final product contain the Y molecular sieve phase, and on the other hand, the dissolved fragments can be used to form a certain amount of ZSM-5 molecular sieve. In addition, by adjusting the amount of the structure directing agent relative to the intermediate Y molecular sieve, the degree of conversion of the Y molecular sieve to the ZSM-5 molecular sieve and the distribution uniformity of the two molecular sieve phases in the composite molecular sieve can be adjusted. In some specific embodiments, the mass ratio of the intermediate Y molecular sieve to the structure directing agent is 0.1-1:0.01-1, for example, 1:0.1-0.4. In some specific embodiments, the mass of the intermediate Y molecular sieve can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints, and accordingly, the mass of the structure directing agent can be 0.01 parts, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 1.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints.

[0031] In the above preparation method, the cation of the structure directing agent can be used as a structure directing agent for the ZSM-5 molecular sieve to promote the formation of the ZSM-5 molecular sieve phase; the anion hydroxide in the alkaline solution of the structure directing agent can dissolve the silicon and aluminum in the Y molecular sieve as the silicon source and aluminum source of the ZSM-5 molecular sieve phase, and on the other hand, it can also provide an alkaline environment to promote the formation of the ZSM-5 molecular sieve phase. By adjusting the type of cation in the structure directing agent, the relative proportion of the two molecular sieve phases in the composite Y molecular sieve can be adjusted. Specifically, the structure directing agent can include one or a combination of two or more of an organic amine, a quaternary ammonium base, and a tertiary ammonium base.

[0032] In the above preparation method, the organic amine may include one or a combination of two or more of tetrapropylammonium bromide, hexadecyltrimethylammonium bromide, triethylamine, and ethylenediamine.

[0033] In the above preparation method, the quaternary ammonium base may include one or a combination of two or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. The TPA+ ions in the quaternary ammonium base can be used as a structure directing agent for the ZSM-5 molecular sieve to promote the formation of the ZSM-5 molecular sieve phase.

[0034] In the above preparation method, the tertiary ammonium base may include choline hydroxide.

[0035] In the above preparation method, the pH range of the alkaline solution of the structure directing agent can be 10-14, specifically, it can be 10, 11, 12, 13, 14 and other specific values, as well as a range with any two of the above specific values ​​as endpoints.

[0036] In the above preparation method, the alkaline solution of the structure directing agent may further include an inorganic base for adjusting the pH value of the solution. In some specific embodiments, the inorganic base may include one or a combination of two or more of LiOH, NaOH, and KOH.

[0037] In some specific embodiments, the solvent used in the alkaline solution of the structure directing agent may include water. Specifically, in the alkaline solution of the structure directing agent, the ratio of the structure directing agent to water can be controlled to be 0.01-1:0.05-5. For example, in parts by mass, the mass of the structure directing agent can be 0.01 parts, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints, and the mass of water can be 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 5.0 parts and other specific values, as well as ranges with any two of the above specific values ​​as endpoints.

[0038] In some specific embodiments, the intermediate Y molecular sieve and the alkaline solution of the structure directing agent are mixed in a manner that the intermediate Y molecular sieve is immersed in the alkaline solution of the structure directing agent. The impregnation method may specifically include an excess impregnation method, an equal volume impregnation method, a multiple impregnation method, an impregnation precipitation method, a fluidized bed spray impregnation method, an impregnation vapor phase impregnation method, a vacuum impregnation method, and a pressurized impregnation method, or a combination of two or more thereof. Alternatively, the intermediate Y molecular sieve and the alkaline solution of the structure directing agent may also be mixed by dropping the alkaline solution of the structure directing agent onto the intermediate Y molecular sieve.

[0039] In the above preparation method, by adjusting the crystallization conditions, the relative ratio of the two molecular sieve phases in the composite molecular sieve can be adjusted. The crystallization temperature can be controlled to be 50-250°C, further controlled to be 90°C-200°C, 100-200°C, and further controlled to be 120-180°C, 120-170°C. Specifically, the crystallization temperature can be 50°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C and other specific values ​​and a range with any two of the above specific values ​​as endpoints.

[0040] In the above preparation method, the crystallization time can be controlled to be 0.1h-120h, for example, 0.1h-24h, 24h-120h, etc. The crystallization time can be specifically 0.1h, 1h, 6h, 12h, 24h, 48h, 72h, 96h, 120h, etc., and a range with any two of the above specific values ​​as endpoints.

[0041] In the above preparation method, the crystallization pressure is generally 0.1-10 MPa.

[0042] In the above preparation method, the crystallization is an in-situ crystallization process. The crystallization includes one or a combination of two or more of solid phase crystallization, steam-assisted crystallization, and normal pressure rotational crystallization. In some embodiments, there is generally no flowing liquid solvent in the crystallization process, and specifically, it can be a solid phase hydrothermal crystallization, a solid-phase hydrothermal crystallization-like process, and the like.

[0043] According to a specific embodiment of the present invention, the above preparation method may include:

[0044] A raw material Y molecular sieve having a silicon-aluminum ratio of ≥2 is mixed with an acidic treatment agent in a mass ratio of 0.1-1:0.01-2 to form a first raw material, and the first raw material is subjected to an acid washing reaction at 75-95° C. for 1 h to 3 h to obtain an intermediate Y molecular sieve, wherein the silicon-aluminum ratio of the intermediate Y molecular sieve is preferably 6-50;

[0045] The intermediate Y molecular sieve and the alkaline solution of the structure directing agent are mixed to form a second raw material, the mass ratio of the intermediate Y molecular sieve to the structure directing agent is 0.1-1:0.01-1, and crystallization is carried out at 50-250° C. for 0.1-120 h to obtain a Y / ZSM-5 composite molecular sieve.

[0046] The present invention also provides a Y / ZSM-5 composite molecular sieve, which is obtained by the preparation method of the Y / ZSM-5 composite molecular sieve.

[0047] In the above Y / ZSM-5 composite molecular sieve, the Y / ZSM-5 composite molecular sieve includes a Y molecular sieve phase and a ZSM-5 molecular sieve phase. The ratio of the Y molecular sieve phase to the ZSM-5 molecular sieve phase in the composite molecular sieve can be controlled by controlling the acidic reaction process, the amount and type of the alkaline solution of the structure directing agent, and the crystallization conditions. In some specific embodiments, the mass content of the ZSM-5 molecular sieve phase in the Y / ZSM-5 composite molecular sieve is greater than 0% and less than or equal to 100% (when it is equal to 100%, the above-mentioned composite molecular sieve is a pure ZSM-5 phase), that is, the ZSM-5 molecular sieve phase can be flexibly changed within the content range of 0-100% by controlling the pickling reaction and the crystallization process. For example, the mass content of the ZSM-5 molecular sieve phase in the Y / ZSM-5 composite molecular sieve can be 0.01%, 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, 99.9%, 100% and other specific values, as well as a range with any two of the above specific values ​​as endpoints.

[0048] When applied to the FCC catalytic field, the composite molecular sieve comprises both a Y molecular sieve phase and a ZSM-5 molecular sieve phase, and the gasoline fraction is further cracked into light olefins by using the coordination between the Y molecular sieve and the ZSM-5 molecular sieve. In some specific embodiments, the mass content of the ZSM-5 molecular sieve phase in the Y / ZSM-5 composite molecular sieve is less than or equal to 99%, and the mass content of the Y molecular sieve phase in the Y / ZSM-5 composite molecular sieve is greater than or equal to 1%.

[0049] In the above-mentioned Y / ZSM-5 composite molecular sieve, the mass ratio of the Y molecular sieve phase to the ZSM-5 molecular sieve phase can further be 40-94:6-60, for example, specific values ​​such as 40:60, 69:31, 80:20, 84:16, 94:6, and a range with any two of the above specific values ​​as endpoints.

[0050] The present invention also provides an FCC catalyst, which includes the above Y / ZSM-5 composite molecular sieve. The above Y / ZSM-5 composite molecular sieve provided by the present invention is applied in the catalytic cracking process to reduce coke, produce more low-carbon olefins and improve total liquid yield.

[0051] The beneficial effects of the present invention include:

[0052] 1. The preparation method provided by the present invention adopts the strategy of "acid washing pretreatment + limited alkali treatment + in-situ crystallization" to prepare Y / ZSM-5 composite molecular sieve, which can not only increase the adaptability of the composition of the raw material Y molecular sieve, but also realize the fine adjustment of the proportion of different phases in the Y / ZSM-5 composite molecular sieve. Moreover, the acid washing and dealuminization process is simple and low in cost, which is conducive to reducing technical costs and facilitating industrial implementation.

[0053] 2. The preparation method provided by the present invention has a simple implementation process and low consumption, and does not require any modification of existing equipment, which is conducive to reducing technical costs, facilitates industrial implementation, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Composite molecular sieve Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 And Y in Comparative Example 1 A -X-ray diffraction pattern of C sample.

[0055] Figure 2 Composite molecular sieve Y A1 / ZSM-5 A1 Scanning electron microscopy images of the samples.

[0056] Figure 3 Composite molecular sieve Y A2 / ZSM-5 A2 Scanning electron microscope image of the sample.

[0057] Figure 4 Composite molecular sieve Y A3 / ZSM-5 A3 Scanning electron microscope image of the sample.

[0058] Figure 5 Composite molecular sieve Y A2 / ZSM-5 A2 -2 and Comparative Example 1 A -X-ray diffraction pattern of C sample.

[0059] Figure 6 Composite molecular sieve Y A2 / ZSM-5 A2 -2Scanning electron microscope image of the sample.

[0060] Figure 7 Composite molecular sieve Y A2 / ZSM-5 A2 -3 and Comparative Example 1 A -X-ray diffraction spectrum of C sample.

[0061] Figure 8 Composite molecular sieve Y A2 / ZSM-5 A2 -3Scanning electron microscope image of the sample.

[0062] Fig. 9 Composite molecular sieve Y A2 / ZSM-5 A2 -4 and Comparative Example 1 A -X-ray diffraction pattern of C sample.

[0063] Fig.10 Composite molecular sieve Y A2 / ZSM-5 A2 -4Scanning electron microscope image of the sample.

[0064] Fig.11 Composite molecular sieve Y A2 / ZSM-5 A2 -5 and Comparative Example 1 A -X-ray diffraction spectrum of C sample.

[0065] Fig.12 Composite molecular sieve Y A2 / ZSM-5 A2 -5 sample scanning electron microscope image.

[0066] Fig.13 Composite molecular sieve Y A2 / ZSM-5 A2 -6 and Comparative Example 1 A -X-ray diffraction spectrum of C sample.

[0067] Fig.14 Composite molecular sieve Y A2 / ZSM-5 A2 -6 sample scanning electron microscope image.

[0068] Fig.15 , Fig.16 Composite molecular sieve Y A3 / ZSM-5 A3 Transmission electron microscopy image of the sample.

[0069] Fig.17 The composite molecular sieve Y prepared in Example 1 A1 / ZSM-5 A1 , Y in Comparative Example 1 A -C molecular sieve, Y in Comparative Example 2 B -X-ray diffraction spectrum of C molecular sieve sample.

[0070] Fig.18 Raw material Y A And obtain composite molecular sieve Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 Low temperature nitrogen adsorption-desorption isotherms.

[0071] Fig.19 Raw material Y A And obtain composite molecular sieve Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 BJH pore size distribution diagram. DETAILED DESCRIPTION

[0072] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0073] The raw material Y molecular sieves in the following examples and comparative examples are all ammonium type molecular sieves.

[0074] In the following experiments, the silicon-aluminum ratio of the molecular sieve was determined by X-ray fluorescence spectrometry.

[0075] Example 1

[0076] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0077] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 30 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2h for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A1 ; Silicon-aluminum ratio: 11.7).

[0078] 2. Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A1Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the pores of the intermediate Y molecular sieve to impregnate evenly. Then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor. The sealed reactor was then placed in a 140°C oven for crystallization for 24 hours. After washing and drying, the Y / ZSM-5 composite molecular sieve product (sample name Y A1 / ZSM-5 A1 ), the X-ray diffraction pattern and scanning electron microscope image of the sample are shown as Figure 1 and Figure 2 shown.

[0079] Example 2

[0080] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0081] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0082] 2. Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A2 Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A2 / ZSM-5 A2 ), the X-ray diffraction pattern and scanning electron microscope image of the sample are shown as Figure 1 and Figure 3 shown.

[0083] Example 3

[0084] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0085] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 70 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2h for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A3 ; Silicon-aluminum ratio: 22.1).

[0086] 2. Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A3 Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A3 / ZSM-5 A3 ), the X-ray diffraction pattern and scanning electron microscope image of the sample are shown as Figure 1 and Figure 4 shown. Fig.15 , Fig.16 This is a transmission electron microscope picture of the sample.

[0087] Example 4

[0088] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0089] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0090] 2. Weigh 0.9 g of 25 wt% tetraethylammonium hydroxide solution and 1 g of acid-washed Y A2 Molecular sieve. At room temperature, 0.9 g of the tetraethylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A2 / ZSM-5 A2-2), the X-ray diffraction pattern and scanning electron microscope image of the sample are as follows Figure 5 and Figure 6 shown.

[0091] Example 5

[0092] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0093] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0094] 2. Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A2 Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly. Then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor. The sealed reactor was then placed in a 180°C oven for crystallization for 24 hours. After washing and drying, the Y / ZSM-5 composite molecular sieve product (sample name Y A2 / ZSM-5 A2 -3), the X-ray diffraction pattern and scanning electron microscope image of the sample are as follows Figure 7 and Figure 8 shown.

[0095] Example 6

[0096] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0097] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0098] 2. Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A2Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 100°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A2 / ZSM-5 A2 -4), the X-ray diffraction pattern and scanning electron microscope image of the sample are as follows Fig. 9 and Fig.10 shown.

[0099] Example 7

[0100] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0101] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0102] 2. Weigh 0.9 g of 15 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A2 Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A2 / ZSM-5 A2 -5), the X-ray diffraction pattern and scanning electron microscope image of the sample are as follows Fig.11 and Fig.12 shown.

[0103] Example 8

[0104] This embodiment provides a Y / ZSM-5 composite molecular sieve, the preparation method of which includes:

[0105] 1. Weigh 20g of ammonium sulfate and 20g of Y molecular sieve (sample name Y A; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.), 50 grams of 10wt% sulfuric acid solution was mixed with 200 grams of water and stirred at 85°C for 2 hours for pickling reaction, and the pickled Y molecular sieve was obtained as the intermediate Y molecular sieve (named Y A2 ; Silicon-aluminum ratio: 14.7).

[0106] 2. Weigh 0.9 g of 40 wt% tetrapropylammonium hydroxide solution and 1 g of acid-washed Y A2 Molecular sieve. At room temperature, 0.9 g of the tetrapropylammonium hydroxide solution was slowly and evenly added to the molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the Y / ZSM-5 composite molecular sieve product (sample name Y) was obtained after washing and drying. A2 / ZSM-5 A2 -6), the X-ray diffraction pattern and scanning electron microscope image of the sample are as follows Fig.13 and Fig.14 shown.

[0107] Comparative Example 1

[0108] This comparative example provides a Y / ZSM-5 composite molecular sieve, the preparation method of which comprises:

[0109] Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of Y molecular sieve (sample name Y A ; Silicon-aluminum ratio: 6.1, USY molecular sieve; Raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.). At room temperature, 0.9 g of the above tetrapropylammonium hydroxide solution was slowly and evenly added to the above molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure-resistant reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the molecular sieve product (sample name Y) was obtained after washing and drying. A -C, where C stands for after crystallization).

[0110] Compared with the preparation method of the above embodiment, no acidic treatment agent is used in the preparation process of this comparative example.

[0111] Comparative Example 2

[0112] This comparative example provides a Y / ZSM-5 composite molecular sieve, the preparation method of which comprises:

[0113] Weigh 0.9 g of 25 wt% tetrapropylammonium hydroxide solution and 1 g of Y molecular sieve (sample name Y B, is USY molecular sieve; silicon-aluminum ratio: 12.5; raw material source: Shandong Qilu Huaxin High-Tech Co., Ltd.). At room temperature, 0.9 g of the above tetrapropylammonium hydroxide solution was slowly and evenly added to the above molecular sieve pores to impregnate evenly, and then the obtained sample was directly transferred into a 5 mL polytetrafluoroethylene lined stainless steel pressure-resistant reactor, and then the sealed reactor was placed in a 140°C oven for crystallization for 24 hours, and the molecular sieve product (sample name Y) was obtained after washing and drying. B -C, where C stands for after crystallization).

[0114] Fig.17 The X-ray diffraction spectra of the molecular sieve products of Example 1, Comparative Example 1 and Comparative Example 2 are shown.

[0115] Fig.18 , Fig.19 Raw material Y A And obtain composite molecular sieve Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 Low-temperature nitrogen adsorption-desorption isotherms and BJH pore size distribution diagram.

[0116] The comparison between Comparative Example 2 and Example 1 demonstrates the promoting effect of the pickling process on solid phase crystallization.

[0117] The raw material Y molecular sieve used in the above examples is all ammonium type molecular sieve, sodium ion concentration is relatively low, and the ammonium salt added in each example is for carrying out ion exchange to the Y molecular sieve, ensuring that the sodium ion content in the Y molecular sieve is extremely low. The anion species (sulfate radical) of the ammonium salt is selected according to the anion species (sulfuric acid) of the acidic treatment agent used for pickling, and it is avoided to introduce new ions in the system, and the anion of the ammonium salt does not affect the amount of the acidic treatment agent participating in the pickling reaction, that is, the addition of the ammonium salt has no obvious effect on the pickling effect. In a specific embodiment of the present invention, it is possible to optionally add or omit ammonium salt according to the specific type of the Y molecular sieve used.

[0118] Test Example 1

[0119] This test example provides the structural characterization results of the molecular sieves prepared in the above examples and comparative examples.

[0120] from Figures 1 to 19 It can be seen that:

[0121] 1. For Example 1 to Example 3, Figure 1It can be seen from the XRD graph that for the sample obtained after in-situ solid phase crystallization, the characteristic diffraction peaks belonging to the Y molecular sieve can be clearly observed at positions such as 2θ=6.30°, 10.34°, 12.15°, 16.00°, and 24.11°. In addition, the characteristic diffraction peaks belonging to the ZSM-5 molecular sieve can be clearly observed at positions such as 2θ=8.00°, 8.95°, and 23.30°. This result proves that the raw material Y molecular sieve has successfully synthesized the Y / ZSM-5 composite molecular sieve through acid washing and in-situ solid phase crystallization. And with the increase of the silicon-aluminum ratio of the intermediate Y molecular sieve after acid washing, the intensity of the diffraction peak belonging to the ZSM-5 molecular sieve in its XRD spectrum gradually increases.

[0122] For the YA molecular sieve with a silicon-aluminum ratio of 6.1 without acid washing (Comparative Example 1), Figure 1 It can be seen that the product of the molecular sieve crystallized under the same conditions only has the characteristic peaks of the Y molecular sieve and does not have the characteristic peaks of the ZSM-5 molecular sieve phase, indicating that the raw material Y molecular sieve that has not been acid-washed will not generate ZSM-5 molecular sieve after crystallization.

[0123] 2. By comparing the products of the intermediate molecular sieve with a silicon-aluminum ratio of 11.7 after acid washing (Example 1) and the commercial molecular sieve with a silicon-aluminum ratio of 12.5 without acid washing under the same crystallization conditions, it was found that even if the silicon-aluminum ratio of the commercially available Y molecular sieve was higher than the silicon-aluminum ratio of the intermediate Y molecular sieve after acid washing, the commercially available high silicon-aluminum ratio Y molecular sieve without acid washing reaction still could not be crystallized to form ZSM-5 molecular sieve through the crystallization process, while the Y molecular sieve with a relatively low silicon-aluminum ratio (compared with the commercially available molecular sieve) after acid washing reaction could be crystallized through the same crystallization process. This is contrary to the existing cognition that "the higher the silicon-aluminum ratio, the deeper the degree of crystallization", indicating that the acid washing treatment of the raw material Y molecular sieve in the present invention can effectively promote the occurrence of the solid-phase crystallization process and contribute to the formation of ZSM-5 molecular sieve.

[0124] 4. From Figure 2 , Figure 4 , Figure 6 It can be seen from the SEM image that in addition to the standard Y-type molecular sieve faujasite shape, a large number of small particles appear on the surface of the Y-type molecular sieve, and the number of small particles increases with the increase of ZSM-5 content. Figure 7 , Figure 8 In the TEM image, it can be observed that these tiny nanoparticles (about 20nm) grow in a dendrite-like manner, and the lattice fringes are very different from those of the original Y-type molecular sieve. Figure 8In the figure, 20 lattice fringes were selected in different regions to calculate the average width of the lattice fringes. It can be seen that in two different regions, the average widths are 0.91nm (ZSM-5 molecular sieve) and 1.37nm (Y molecular sieve), respectively, proving that the crystallized product contains both Y molecular sieve phase and ZSM-5 molecular sieve phase. Combined with the XRD spectrum, it can be seen that these tiny nanoparticles in the electron microscope image are newly generated ZSM-5 molecular sieves, proving that ZSM-5 in the composite molecular sieve exists in nano form.

[0125] according to Fig.18 The adsorption-desorption isotherms shown in the figure are all type IV adsorption isotherms for the crystallized samples of Examples 1 to 3, and all have hysteresis loops, indicating that ink bottle-shaped mesopores exist in the crystallized composite molecular sieve samples. A The decrease in the adsorption amount of the Y / ZSM-5 composite molecular sieve sample obtained after acid washing and solid phase crystallization in the low pressure zone indicates that the solid phase crystallization process will cause a decrease in the micropore content. Fig.19 From the pore size distribution curve, we can see that the mesopore size distribution of the sample becomes significantly wider after the crystallization treatment.

[0126] Table 1 shows the mass ratio of acid to molecular sieve during the pickling reaction in the above embodiments and comparative examples (hereinafter referred to as the pickling acid amount), the silicon-aluminum ratio of the Y molecular sieve before crystallization, and the mass ratio of the Y molecular sieve phase to the ZSM-5 molecular sieve phase in the final molecular sieve sample.

[0127] The mass ratio of the Y molecular sieve phase to the ZSM-5 molecular sieve phase in the composite molecular sieve can be calculated based on the characteristic peak area of ​​the molecular sieve phase. A mixture of a standard Y molecular sieve and a standard ZSM-5 molecular sieve in a mass ratio of 1:1 is used as a standard sample, and the diffraction peak area is selected for comparison. The mass ratio is recorded as 1:1, and then the calculation is performed based on the diffraction conditions of each sample to be tested.

[0128] Table 1

[0129]

[0130] As can be seen from Table 1, the present invention can obtain a composite molecular sieve having both a Y molecular sieve phase and a ZSM-5 molecular sieve phase by treating the Y molecular sieve with an acidic treatment agent and a structure directing agent respectively. In addition, the present invention can continuously and accurately adjust the silicon-aluminum ratio of the Y molecular sieve by treating the Y molecular sieve with an acidic treatment agent.

[0131] Furthermore, Example 4 changes the type of structure directing agent relative to the preparation method of Example 2. The ion volume of tetraethylammonium hydroxide in Example 4 is smaller than the ion volume of tetrapropylammonium hydroxide in Example 2. Tetraethylammonium hydroxide can convert the Y molecular sieve with a lower silicon-aluminum ratio into a ZSM-5 molecular sieve in the framework equilibrium. Therefore, under the same silicon-aluminum ratio of the raw material Y molecular sieve and the silicon-aluminum ratio of the intermediate Y molecular sieve, the conversion ratio of the Y molecular sieve to the ZSM-5 molecular sieve obtained by using tetraethylammonium hydroxide as the structure directing agent is higher. The above results show that the present invention can effectively adjust the relative ratio of the two molecular sieve phases in the composite molecular sieve by adjusting the type of the structure directing agent.

[0132] The crystallization temperature of Example 5 and Example 6 is changed relative to the preparation method of Example 2. From the comparison of the scanning electron microscope images, it can be seen that in the composite molecular sieves of Example 6 and Example 2 with lower crystallization temperatures, fine nanocrystals can be observed on the surface of the Y-type molecular sieve, and the dissolution phenomenon is more obvious and the fragmented substances increase in the composite molecular sieve of Example 5 with increased temperature. From the results of Table 1, it can be seen that in Example 2, Example 5, and Example 6, the conversion ratio of the Y molecular sieve to the ZSM-5 molecular sieve is higher with the increase of the crystallization temperature. The above results can illustrate that by adjusting the crystallization temperature, the dissolution of silicon and aluminum of the Y molecular sieve during the crystallization process can be adjusted, thereby controlling the proportion of the formed ZSM-5 molecular sieve phase.

[0133] In Example 7 and Example 8, the amount of the structure directing agent is changed relative to the preparation method of Example 2. Combining the XRD diagram and the results of Table 1, it can be seen that the ratio of the two phases in Example 7 and Example 8 is significantly different under the same conditions after changing the amount of the structure directing agent. In Example 7, Example 2, and Example 8, as the amount of tetrapropylammonium hydroxide added increases, the conversion ratio from Y molecular sieve to ZSM-5 molecular sieve increases. From the comparison of the scanning electron microscope images, it can be seen that the Y-type molecular sieve in Example 7 with a reduced amount of structure directing agent can also form a small amount of nanoparticles, while in Example 8 with an increased amount of structure directing agent, the Y-type molecular sieve is surrounded by more nanoparticles. The above results show that by adjusting the amount of the structure directing agent, the dissolution of Y and the growth of ZSM-5 during the crystallization process can be adjusted, thereby controlling the proportion of the formed ZSM-5 molecular sieve phase.

[0134] Test Example 2

[0135] This test example provides the structural characterization results of the molecular sieves prepared in the above examples and comparative examples.

[0136] Table 2 shows the Y / ZSM-5 composite molecular sieves prepared by acid washing reaction in the above examples and the raw material Y AIn Table 2, a is the BET total specific surface area (BET surface area); b is the result obtained by the t-plot method (t-plot method); c represents the mesopore specific surface area and mesopore volume calculation method: S meso =S BET -S micro ,V meso =V total -V micro .

[0137] Table 2 Raw material Y A And obtain composite molecular sieve Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 , Y A2 / ZSM-5 A2 -2, Y A2 / ZSM-5 A2 -3. Y A2 / ZSM-5 A2 -4 pore structure data

[0138]

[0139] It can be seen from Table 2 that the Y A1 / ZSM-5 A1 , Y A2 / ZSM-5 A2 , Y A3 / ZSM-5 A3 The mesopore specific surface area and pore volume all show an increase. And compared with the raw material Y molecular sieve, the composite molecular sieve sample with a deeper solid phase crystallization depth and a higher ZSM-5 content has a greater increase in mesopore volume. The above data prove that the present invention obtains a USY / ZSM-5 composite molecular sieve with abundant mesopores through acidity and solid phase crystallization.

[0140] Test Example 3

[0141] This test example provides a performance test of the Y / ZSM-5 composite molecular sieve sample prepared in Example 2.

[0142] Table 3 is the composite molecular sieve Y A2 / ZSM-5 A2 And the performance evaluation results of catalytic cracking micro-reactor of mechanical mixture and raw material USY in corresponding proportions.

[0143] Catalyst preparation: Dry and cool the molecular sieve sample to be tested, stir kaolin, molecular sieve, silica sol and water at 100℃ for 4h and mix them evenly according to the mass ratio of 5:4:2:20, dry them at 100℃ overnight, and then hydrothermally age them at 100℃ for 4h. The obtained sample is pressed into tablets at 20MPa and sieved into 20-40 mesh to obtain the catalyst used in the FCC micro-reactor. Before the catalytic reaction evaluation, fill the catalyst bed, increase the temperature to 100℃ at a rate of 2℃ / min in a nitrogen atmosphere, keep the temperature at 100℃ for 2h, increase the temperature to 550℃ at a rate of 2℃ / min, calcine at 550℃ for 2h, and then cool naturally to the reaction temperature for use. This process is the in-situ activation of the catalyst.

[0144] Catalytic cracking: In this experiment, the catalytic performance of the prepared molecular sieve catalyst was evaluated using a Beijing Weikendu catalytic cracking fixed-bed reactor. Nitrogen was used as a carrier gas, and the feed rate was changed by adjusting the nitrogen flow rate, thereby adjusting the reaction space velocity. The inner diameter of the reaction tube was 2 cm, and the catalyst loading was 5 g.

[0145] Operating parameters: reaction temperature: 510°C; regeneration temperature: 650°C; carrier gas flow rate: 200 mL / min

[0146] Steps:

[0147] (1) Using quartz sand and quartz wool to fix the molecular sieve particles at the end point of the thermocouple in the middle of the reaction tube;

[0148] (2) Install and fix the reaction tube, check the air tightness of the device and related insulation, and ensure that the air tightness and insulation performance of each pipeline are intact;

[0149] (3) nitrogen was introduced into the reaction tube, and the temperature was gradually raised to 510° C. to activate the catalyst in situ;

[0150] (4) adjusting the carrier gas flow rate to an appropriate level, and passing the feedstock oil into the reaction tube to contact the catalyst to start the reaction;

[0151] (5) After the reaction is completed, the liquid and gas phase products are collected, subjected to chromatographic analysis, and the product distribution is calculated;

[0152] (6) Start the aging program and raise the temperature to 650°C for 1 hour, then repeat steps (3), (4), and (5) for cyclic evaluation.

[0153] The Y-type molecular sieve (corresponding to the Y molecular sieve phase in the composite molecular sieve of Example 2) and the ZSM-5 molecular sieve (corresponding to the ZSM-5 molecular sieve phase in the composite molecular sieve of Example 2) were mechanically mixed in a mass ratio of 84:16 to obtain comparative sample 2.

[0154] The raw material Y molecular sieve (USY molecular sieve in Example 2) used to prepare the composite molecular sieve is used as comparative sample 1.

[0155] Table 3 Composite molecular sieve Y A2 / ZSM-5 A2 And the corresponding proportion of mechanical mixture and raw material USY catalytic cracking micro-reactor performance evaluation results

[0156]

[0157] As can be seen from Table 2, the comparative sample 2 formed by mechanically mixing the two molecular sieves increased the coke yield by 0.44 and the propylene yield by 2.11% relative to the conventional USY molecular sieve (comparative sample 1); and the Y / ZSM-5 composite molecular sieve of Example 2 can not only further improve the propylene yield, but also significantly reduce the coke yield (the reduction is up to 1.11%). The existing industrial catalytic cracking catalyst has a total liquid yield (corresponding to "liquefied gas + gasoline + diesel" in Table 3) of 83-86%, a coke yield of 6-10%, and a propylene yield of about 5%. It can be seen that the catalytic performance of the Y / ZSM-5 composite molecular sieve of Example 2 is also significantly improved relative to the catalytic performance of the existing industrial catalytic cracking catalyst.

[0158] Table 3 can prove that, compared with the existing FCC catalyst, the Y / ZSM-5 composite molecular sieve provided by the present invention has a more excellent effect in improving propylene yield, reducing coke, etc., which can prove that the preparation method of the present invention can regulate the structure of the composite molecular sieve, and the Y / ZSM-5 composite molecular sieve obtained thereby has excellent catalytic performance.

[0159] The above results show that the present invention can appropriately remove the framework aluminum in the molecular sieve and increase the silicon-aluminum ratio of the Y molecular sieve by treating the raw material Y molecular sieve with an acidic treatment agent. The intermediate molecular sieve thus obtained is mixed with a treatment agent that can have a structure-directing agent effect and further interacts with each other, dissolving, nucleating, and crystallizing part of the Y molecular sieve framework under certain hydrothermal conditions to generate a multi-level pore Y / nano ZSM-5 composite molecular sieve. The Y molecular sieve silicon-aluminum ratio is controlled by regulating the acid washing reaction conditions, and then the ratio of the two-phase molecular sieve in the synthetic Y / ZSM-5 composite molecular sieve is regulated to improve the catalytic performance of the Y / ZSM-5 composite molecular sieve.

Claims

1. A method for preparing a Y / ZSM-5 composite molecular sieve, the method comprising: Mixing a raw material Y molecular sieve with an acidic treatment agent to form a first raw material, and subjecting the first raw material to an acid washing reaction to obtain an intermediate Y molecular sieve; The intermediate Y molecular sieve is mixed with an alkaline solution of a structure directing agent to form a second raw material, and crystallized to obtain the Y / ZSM-5 composite molecular sieve; Wherein, the silicon-aluminum ratio of the raw material Y molecular sieve is greater than or equal to 2, The acidic treatment agent includes acid, and the mass ratio of the raw material Y molecular sieve to the acid is 0.1-1:0.01-2.

2. The preparation method according to claim 1, wherein The temperature of the pickling reaction is 75° C.-95° C., and the time of the pickling reaction is 1 h-3 h.

3. The preparation method according to claim 1, wherein The first raw material also includes ammonium salt, and the mass ratio of the raw material Y molecular sieve, acid, and ammonium salt is 0.1-1:0.01-2:0-1.

4. The preparation method according to claim 3, wherein The ammonium salt includes one or a combination of two or more of ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium oxalate, ammonium fluoride, and ammonium fluorosilicate.

5. The preparation method according to claim 1, wherein The silicon-to-aluminum ratio of the intermediate Y molecular sieve is 6-50.

6. The preparation method according to claim 1, wherein The mass ratio of the intermediate Y molecular sieve to the structure directing agent is 0.1-1:0.01-1; Preferably, the mass ratio of the intermediate Y molecular sieve to the structure directing agent is 1:0.1-0.

4.

7. The preparation method according to claim 1 or 6, wherein: The structure directing agent includes one or a combination of two or more of an organic amine, a quaternary ammonium base, and a tertiary amine base.

8. The preparation method according to claim 7, wherein: The organic amine includes one or a combination of two or more of tetrapropylammonium bromide, hexadecyltrimethylammonium bromide, triethylamine, and ethylenediamine.

9. The preparation method according to claim 7, wherein: The quaternary ammonium base includes one or a combination of two or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

10. The preparation method according to claim 7, wherein: The tertiary amine base includes choline hydroxide.

11. The preparation method according to claim 1, wherein: The crystallization temperature is 50-250°C, and the crystallization time is 0.1-120h; Preferably, the crystallization temperature is 90-200°C.

12. A Y / ZSM-5 composite molecular sieve obtained by the preparation method according to any one of claims 1 to 11.

13. The Y / ZSM-5 composite molecular sieve according to claim 12, wherein: The Y / ZSM-5 composite molecular sieve comprises a Y molecular sieve phase and a ZSM-5 molecular sieve phase, and the mass content of the Y molecular sieve phase in the Y / ZSM-5 composite molecular sieve is greater than or equal to 1%; Preferably, the mass ratio of the Y molecular sieve phase to the ZSM-5 molecular sieve phase is 40-94:6-60.

14. An FCC catalyst comprising the Y / ZSM-5 composite molecular sieve according to claim 12 or 13.

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